In process piping the need for flow conditioners downstream of pipe elbows, valves and other flow interrupting devices is well documented in many prior art patents. Using an orifice plate flow meter with multiple apertures to self-condition disturbed and non-linear flow by averaging the differential pressure drops across a plate is the subject of U.S. Pat. No. 7,284,450. In the '450 patent the background of the problem solved by the averaging orifice plate is set forth and is incorporated herein by reference.
Following some period of use of the averaging orifice plate flow element disclosed in the '450 patent it has been discovered that some beta ratio designs of the flow element create a blockage along the walls of the fluid carrying conduit. Such blockage diverts abrasive particulates that would otherwise travel along the pipe wall into the interior of the fluid stream, causing the particles to erode the sharp upstream edges of the orifices and thus depreciate the accuracy of the flow rate measurement. The upstream edges are especially susceptible to erosion because they are not only sharp but they are also thin, the downstream side of the edge being beveled to allow expansion of the fluid after it passes through the orifice.
Accordingly, it is the primary object of the present invention to prevent fluid blockage by positioning the openings in the orifice plate proximate the pipe wall.
Another object of the invention is to position the openings of an averaging orifice plate so that particulates, as well as liquids in gas applications, can pass freely through the flow meter with minimal impact on the sharp edges of the plate's orifices, whether the fluid flow in the pipe is annular or stratified.
A still further object of the invention is to substantially reduce the extent of orifice edges in an averaging orifice plate flow meter that are subject to erosion.
Other and still further objects, features and advantages of the present invention will be apparent upon a reading of the following detailed description of the invention, taken in conjunction with the drawings.